Conventionally, if a testing procedure is performed to determine an RF circuit characteristic of an RF device while a radiofrequency (RF) circuit of the RF device, e.g. an antenna, is working, it is likely to interfere the function of the RF circuit and thus adversely affect the communication quality. Therefore, testing an RF circuit to determine the RF circuit characteristic of the RF device is generally conducted in a specific testing mode instead of a normal working mode. In other words, the RF circuit characteristic is measured by a testing process but not in a normal process. It would cause inconvenience for testing operations. Moreover, for a DC-Ground RF circuit whose impedance characteristic is grounded in direct-current (DC) frequency but non-grounded in other frequency, a short-circuit problem cannot be screened out by a DC voltage test. Likewise, for a DC-Open RF circuit whose impedance characteristic is open-circuit in direct-current (DC) frequency but non-open-circuit in other frequency, a disconnection problem cannot be screened out by a DC voltage measurement.
The above-mentioned defects make maintenance of an RF circuit problematic.